WeldConstraint Bug with Model CFrame And Placement System

I have a weird problem with my model move system.

With normal “Weld” i have just a slide problem.
But with “Weld Constraint” i have a model sync problem.

A video is better then 1 Thousand Words
Video The Video have a weight of 23Mb/s so i can’t upload it here. Edit : Thanks Google for the low quality…

I set the model pos on the client and the server with CFrame

Thanks for all trying to help me